INSECT COMMUNITIES 279 



of them pass the winter in company in some sheltered 

 spot. But it is not apparently thus that the true social 

 communities have been elaborated ; these, like human 

 states, have their origin in the family. For these com- 

 munities three conditions are necessary — a nest large 

 enough for a number of insects, a close grouping of the 

 cells, and an association between mother and offspring in 

 the perfect state. The last condition will be brought about 

 by the emergence of the older insects of the brood while 

 the mother is still occupied with the younger larvae or 

 their cells. In a single species of solitary bee (Halictus 

 quadristrigatus) these conditions are almost fulfilled, but 

 the first young insects to appear are males, and when the 

 females are developed the mother dies." 



The small bees of the genus Halictus are in many 

 respects more advanced than any of their solitary con- 

 geners, and among certain species Fabre has observed a 

 marked tendency towards co-operation. A number of 

 females combine to form a common burrow which gives 

 access to the various groups of cells. There is also a 

 vestibule, or widening of the burrow near the opening, 

 which enables the bees to pass one another easily as they 

 go in and out, while a sentinel bee is posted to guard the 

 entrance. But there is no worker class. Each female 

 constructs and provisions her own set of cells after the 

 manner of solitary bees in general. The condition of 

 Halictus, indeed, has been aptly compared to that of 

 families occupying a model dwelling, each separate and 

 distinct, but using a common stair and the same street 

 door. In one other point the genus Halictus foreshadows 

 the true social groups. Usually the males and females 

 emerge late in the season, and although pairing takes 

 place, no new burrows are formed. The males perish as 

 winter approaches, but the females retire to the old 



